High-speed wood-boring bit



Feb; 27, 1951 E. H. SMITH 2,543,206

HIGH-SPEED WOOD BORING BIT Filed July 23, 1948 INVENTOR) Esron H. SMITH,

TTORNEY.

Patented Feb. 27, 1951 HIGH-SPEED WOOD-B G BIT Eston H. Smith, Indianapolis, Ind., assignor to Benjamin B. Aufderheide, Indianapolis, Ind.

Application Ju y 23, 1948, Serial No. 40,378

3 Claims.

This invention relates to a wood boring bil intended to be operated at relatively high speeds up to two thousand to three thousand five hundred revolutions per minute such as will prevail in the usual electric portable drill or in the stationary drill press. The invention embodies many advantages among which are to be found the absence of heating of the bit even though running at high speed; the absence of a screw feed to cause the bit to travel into the wood; the possibility of drilling or boring holes at angles to each other, and intersecting one hole with another, and even to boring of overlapping holes all without splitting end grain sections and the like; absence of chattering or squealing in the drilling operation; the formation of a perfectly cylindrical hole with the wall of that hole smooth and relatively polished; and most importantly, an operation with very low torque at the, h gh speeds.

These and many other objects and advantages of the invention will become apparent to those skilled in the art in the following description of one particular form of the bit as illustrated in the accompanying drawing, in which Fig. 1 is a view in edge elevation of a bit embodying the invention;

Fig. 2, a view in elevation from the flat side;

Fig. 3, a view in edge elevation 180 degrees removed from that view as shown in Fig. 1;

Fig. 4, a transverse section on the line 4-{i in Fig. 2; and

Fig. 5, a transverse section on the line 5 in Fig. 2.

Like characters of reference indicate like parts throughout the several views in the drawing. It is to be understood that the bit will be supplied to the trade in a wide range of sizes as may be desired for drilling the particular diameter holes required. The size of the bit illustrated in the accompanying drawing is that for boring a inch hole.

A stem it is provided to have an upper end portion ll formed to fit Within the usual chuck of the drill. In the form herein shown, this end portion H is provided with a number of flats l2 in order to hold the stem ll] against rotation within the chuck.

At the lower end of the stem LB there is provided a flat portion l3 which is an integral portion of the stem I B, and flares outwardly laterally therefrom and is reduced to the desired thickness. From the lower end of this fiat portion i3 and centered on the axis of the stem H] is a second flat portion 14 here and after termed the pilot.

The flat portion I3 is centered on the axis oi. the stem It. The vertical edges of this flat portion 13, namely the edges I5 and I6 must be exactly parallel. Furthermore these edges l5 and 56 must each be at exactly degrees to both the front and back faces of the flat portion It. From the extreme top ends of these edges l 5 and It, the

stem I0 is joined by the long radius fillets l1 and I8. Then between the stem iii and the opposite faces of the fiat portion I3 the stem It is carried down by the reducing portions 19 and 20 to terminate as suggested in Fig. 2 in a fan shape extending downwardly from the junctures of the fillets I1 and i8 with the top ends of the edges l5 and i6 whereby the flat portion i3 is reinforced in effect by these thickened portions l9 and 23 below the upper corners 2i and 22 of the respective edges l5 and it. It is extremely important however that these edges [5 and i6 be of exactly constant width from top to bottom, else the holes will not be bored true, and chattering and heating might develop.

The pilot I 4 has parallel edges 23 and 25 extending downwardly from the under edge portion of the fiat 13. These edges 23 and 26 must be exactly parallel one to the other .and also be at exactly right angles to the front and back faces of the pilot M. The lower ends of these edges 23 and 24 terminate respectively at the lines 25 and 25, fr wh h t pi M has ed es 2 and 28 e tend n downward y and one toward the t e t the a is ext nding oug the stem t to form a lower point. This lower point of the pi ot l4 terminates in a line 29 which is t right an les to the axis o th s em 1 B- In order to better understand the proportioning of the various parts of the bit, for the particular size of inch bit .(as above indicated the proportions will vary for each size of the bit in some respects) the vertical height .of the edges iii and I6 is substantially M; of an inch to the corners and 22; the over-all height .of the pilot from the l ne 29 to t e un er edg portion of th fiat 3 substantially one inch; the transverse width e o on 43 is 3/4. of an n h; he tran v se width f the pi ot 4 is A of an inch; and the a thickness of the flat portion 11 3 of the pilot is is substantially eof an inch.

On each side .of the pilot M, at its upper end, there are provided the cutting edges 39 and 3i, which constitute the under edge portions of the flat l3 extending respectively from the upper ends of the pilot edges 23 and 24. These cutting edges 30 and ,3l are at exactly right angles to the edges 23 and 24, and hence at right angles to the extended axis of the stem ID.

The bit herein shown is intended to be turned in a clockwise direction. The edges 30 and 3! are ground to have a clearance or bottom rake of from 10 to 20 degrees, the top rake being zero. Then the included angle between the pilot lower edges 2'! and 28 is between 55 and 60 degrees. Each of these pilot edges 27 and 28 is given a clearance rake of from 8 to 10 degrees. These clearance or bottom rakes of the edges 30, 3|, and 21, 28 are critical within the ranges indicated. The vertical or axial length of the flat portion 13 and of the pilot [4 are provided to be such that the edges 38, 3!, and 2'1, 28, may be reground from time to time as the cutting corners may be dulled through usage. In so sharpening the bit, the relative proportions however will be maintained. The diameter of the stem is approximately /4 of aninch for the size of the bit above indicated. By reason of this relatively small diameter of the stem, 10, there will be ample room for the shavings or chips cut by the edges 35, 3|, and 21, 28 to be ejected upwardly through the hole without having to employ the usual augur or screw form of bit.

By reason of the long length of the pilot [4, the bit may be employed to enter wood at positions diagonally of the surface at relatively low angles. In fact the limiting angle would be that angle from the side edges 2'! or 28 with the corners of the fiat portion [3 between the edges I5, 36 or l6, 3! as the case may be.

The angles for the clearance or bottom rake of the pilot edges 27 and 28 must be within the limits indicated in order that the hole will be round and true. In other words the pilot determines the centering of the bit throughout the boring operation until the pilot passes through the wood if the hole is bored that deep. Then the cutting edges 38 and 3| in fact exert a scraping action in a rotary manner rather than actually cutting or lifting a shaving or chip as is the usual cutting action in other types of bits. This particular scraping action permits the bit to be operated at the high speed but with a very low torque, and yet be very effective and speedy in drilling the hole desired.

Emphasis as above indicated is placed upon maintaining the edges l5, l6 and 23, 24 in exact parallel alignment in those pairs, parallel with the extended axis through the stem l0, and at right angles to the faces of the flat portion l3 and of the pilot M. This arrangement of these edges cause those edges to have their faces to be positioned as cords across the circle of the hole being bored. In other words both the leading and trailing corners of those edges are in contact with the wall of the hole being bored, first the hole bored initially by the pilot l4, and then the full sized hole being bored by the edges 30 and 3!. This results in a reaming action to smooth the hole as the bit travels therein. The parallel edged, flat pilot l4, permits the boring of holes in overlapping relation, and in crossing through a previously drilled hole. Not only is this type or design of bit peculiarly effective in boring in wood, but it is ideal for boring fiber and plastic materials without digging or tearing out.

Reference is made to my co-pending application Serial Number 737,765, filed March 28, 1947, of which this application is a continuation in part.

While I have herein shown and described my invention in the one particular form and in the particularly set out relative proportions, it is obvious that structural changes and sizes may be employed and varied respectively without departing from the spirit of the invention, and I therefore do not desire to be limited to that exact form beyond the limitations which may be imposed by the following claims.

I claim:

1. A high speed wood boring bit comprising a driving stem; a fiat plate portion, from the upper part of which said stem centrally emerges; a flat plate pilot extending centrally from the lower end of said portion with its side faces positioned in the planes of the corresponding faces of said portion, said planes being parallel to the axis of said stem; the vertical edge faces of said portion and of said pilot bein disposed at ninety degrees to said portion and pilot faces; said pilot having a bottom pointed end defined by diagonally disposed edge faces, the included angle between which faces ranges from 55 to 60 degrees, said diagonal faces each having a clearance angle in respect to said side faces ranging between 8 to 10 degrees; and cutting edges along the bottom of said plate portion and extending respectively degrees outwardly from the top ends of the vertical edges of said pilot, said cutting edges having a clearance angle of between 15 and 20 degrees.

2. A high speed wood boring bit comprising a driving stem; a flat plate portion, from the upper part of which said stem centrally emerges; a flat plate pilot extending centrally from the lower end of said portion with its side faces positioned in the planes of the corresponding faces of said portion, said planes being parallel to the axis of said stem; the vertical edge faces of said portion and of said pilot being disposed at ninety degrees to said portion and pilot faces; said pilot having a bottom pointed end defined by diagonally disposed edge faces, the included angle between which faces ranges from 55 to 60 degrees, said diagonal face each having a clearance angle in respect to said side faces ranging between 8 to 10 degrees; and cutting edges along the bottom of said plate portion and extending respectively 90 degrees outwardly from the top ends of the vertical edges of said pilot, said cutting edges having a clearance angle in respect to said side faces of between 15 and 20 degrees; said vertical edge faces of both said portion and of said pilot bein centered from and parallel to said stem axis.

3. A high speed wood boring bit comprising a driving stem; a plate portion, from the upper part of which, said stem centrally emerges; a plate pilot extending centrally from the lower edge of said plate portion, axially of said stem; all points in the lines of junctures of the front and back faces with the side edge faces of the plate portion being at the same common radial distance from the axis of said stem; said pilot being less in width than said plate portion and having a bottom pointed end defined by diagonally disposed bottom edge faces, the included angle between which faces ranges from 55 to 60 degrees, said bottom edge faces having a clearance angle in respect to the pilot front and back faces ranging between 8 to 10 degrees; and cutting edges along the bottom of said plate portion extending from said pilot respectively 90 degrees to said axis, said plate portion cutting edges having a clearance angle in respect to the front and back faces of between 15 and 20 degrees; said plate pilot having all points in the lines of junctures between its front and back faces and its edge faces at a common radius from said axis.

ESTON H. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 

